Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 03-04-2021, 18:40   #16
Registered User

Join Date: Dec 2009
Location: Australia
Boat: BUILT!!! Roberts Mauritius 43ft
Posts: 3,604
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by Jim Cate View Post
Adding 200 lbs at the top of the existing 3000 lb ballast will not, IMO, have a "great effect" on the righting moment... one that the PO will be able to discern in his use of the boat.

Jim
Jim

I think I should have said 400lb but anyway I think we would have to have a computerized brain to work out all the variables of boat stability and come up with an ideal boat.

I don't want to breach copyright so can only cut-n-paste a very small section of an excellent article (but the whole article is really well worth reading)

"It is helpful to perform a few basic calculations... For example, assume we have 2,000 pounds of ballast located 5 feet from the roll axis. This will provide a Righting Moment (Torque) of 5 * 2,000 = 10,000 lb-ft however it will yield a Roll Moment of Inertia of 5^4 * 2,000 = 1,250,000 lb-ft^ Much more dramatic is to consider a 200 pound mast having its CG located 25 feet above the roll axis. The mast will introduce a Heeling Moment of 25 * 200 = 5,000 lb-ft, but will have a Roll Moment of Inertia of 25^4 * 200 = 78,125,000 lb-ft^4.

In this example, the mast exerts exactly half the static moment (torque) as compared to the ballast, but although the mast has only one tenth the mass of the ballast, by virtue of its distance from the roll axis the mast is some 62.5 times more effective at resisting being put into motion...!! It is by this simple example that we can observe the extraordinary benefits conferred by well-distributed masses
.
Many years ago during the Fastnet Race, rigorous analyses done after the loss of many vessels revealed that the boats which had concentrated ballast, light structure, and very light rigging suffered excessively due to their harsh rolling motions which caused many dismastings with consequent capsizes, as well as widespread seasickness and inability to function.

By comparison, boats with heavier structure, lesser "ballast rati......."

http://www.kastenmarine.com/beam_vs_ballast.htm
coopec43 is offline   Reply With Quote
Old 04-04-2021, 17:42   #17
Registered User

Join Date: Sep 2012
Location: Tasmania
Boat: Cutter rigged Tahitiana
Posts: 45
Re: Stolen ballast, how important is it really?

For anyone interested; have a read of 'Seaworthiness, the Forgotten Factor' by CA Marchaj - brilliant and accessible exposition of the interplay of all factors influencing stability and sailability.
Christian W. is offline   Reply With Quote
Old 04-04-2021, 17:50   #18
Registered User
 
skkeith's Avatar

Join Date: Mar 2013
Location: Santa Cruz
Boat: 1975 Isander 28
Posts: 132
Re: Stolen ballast, how important is it really?

I actually have lead and not afraid to smelt it, plus I am already a retarded juvenile, so no problem there. But there are issues like how to design the molds, how to fasten the blocks, also how to inspect and clean the keel-bolts underneath regularly, etc. makes me reluctant to actually do this unless someone gives me really good reason to. The crack about jail time was tounge and cheek, I just don't want to do it unless it really will help measurably.

Could this ballast help with either the weather helm into the wind or broaching when running? These are the two areas that could use some improvement.
skkeith is offline   Reply With Quote
Old 04-04-2021, 19:00   #19
Moderator
 
Don C L's Avatar

Join Date: Sep 2014
Location: Channel Islands, CA
Boat: 1962 Columbia 29 MK 1 #37
Posts: 14,305
Images: 66
Re: Stolen ballast, how important is it really?

As an owner of a tender boat, I have considered adding ballast. In fact the builders of my boat did add a thousand pounds more of lead after a couple years of production. But the designer wasn't dumb, he knew what he was doing in calculations. Now it may be that adding that weight does give it some measure of stiffness that may benefit it going upwind. YOur bilge is kinda shallow though so it wasn't much below the waterline. Still, any weight below the waterline is a good thing. Your former owner may have been trying for a small racing advantage, but your boat should sail fine as is. If you need to balance out the engine you might try buying 200' of 1/4 chain and stow it under the v-berth.
My rigger friend keeps bugging me to get more ballast and his argument is that any weight below the waterline helps to lower the whole boat which lowers the center of gravity and improves stiffness.
__________________
DL
Pythagoras
1962 Columbia 29 MKI #37
Don C L is offline   Reply With Quote
Old 04-04-2021, 19:46   #20
Registered User

Join Date: Dec 2009
Location: Australia
Boat: BUILT!!! Roberts Mauritius 43ft
Posts: 3,604
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by skkeith View Post
I actually have lead and not afraid to smelt it, plus I am already a retarded juvenile, so no problem there. But there are issues like how to design the molds, how to fasten the blocks, also how to inspect and clean the keel-bolts underneath regularly, etc. makes me reluctant to actually do this unless someone gives me really good reason to. The crack about jail time was tounge and cheek, I just don't want to do it unless it really will help measurably.

Could this ballast help with either the weather helm into the wind or broaching when running? These are the two areas that could use some improvement.

My mold was just a steel "U" beam and I used sheet-metal "dividers" hammered in at the appropriate length. By raising one end I was able to make tapered "ingots" which I used appropriately to follow the shape of the keel. Some of the ingots in the background I bought





Attached Thumbnails
Click image for larger version

Name:	IMG_1926 (1).jpg
Views:	64
Size:	459.7 KB
ID:	235912  
coopec43 is offline   Reply With Quote
Old 05-04-2021, 03:18   #21
Marine Service Provider

Join Date: Dec 2010
Location: Little Compton, RI
Boat: Cape George 31
Posts: 2,978
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by coopec43 View Post
Jim

I think I should have said 400lb but anyway I think we would have to have a computerized brain to work out all the variables of boat stability and come up with an ideal boat.

I don't want to breach copyright so can only cut-n-paste a very small section of an excellent article (but the whole article is really well worth reading)

"It is helpful to perform a few basic calculations... For example, assume we have 2,000 pounds of ballast located 5 feet from the roll axis. This will provide a Righting Moment (Torque) of 5 * 2,000 = 10,000 lb-ft however it will yield a Roll Moment of Inertia of 5^4 * 2,000 = 1,250,000 lb-ft^ Much more dramatic is to consider a 200 pound mast having its CG located 25 feet above the roll axis. The mast will introduce a Heeling Moment of 25 * 200 = 5,000 lb-ft, but will have a Roll Moment of Inertia of 25^4 * 200 = 78,125,000 lb-ft^4.

In this example, the mast exerts exactly half the static moment (torque) as compared to the ballast, but although the mast has only one tenth the mass of the ballast, by virtue of its distance from the roll axis the mast is some 62.5 times more effective at resisting being put into motion...!! It is by this simple example that we can observe the extraordinary benefits conferred by well-distributed masses
.
Many years ago during the Fastnet Race, rigorous analyses done after the loss of many vessels revealed that the boats which had concentrated ballast, light structure, and very light rigging suffered excessively due to their harsh rolling motions which caused many dismastings with consequent capsizes, as well as widespread seasickness and inability to function.

By comparison, boats with heavier structure, lesser "ballast rati......."

http://www.kastenmarine.com/beam_vs_ballast.htm
IIRC, Skene advocates bolting some of your ballast to the underside of the side decks to bring the weight UP and make the roll period better. Seems counterintuitive to me, but Skene was very well regarded even after his day had passed.
__________________
Ben
zartmancruising.com
Benz is offline   Reply With Quote
Old 05-04-2021, 03:20   #22
Marine Service Provider

Join Date: Dec 2010
Location: Little Compton, RI
Boat: Cape George 31
Posts: 2,978
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by coopec43 View Post
My mold was just a steel "U" beam and I used sheet-metal "dividers" hammered in at the appropriate length. By raising one end I was able to make tapered "ingots" which I used appropriately to follow the shape of the keel. Some of the ingots in the background I bought





Cooper, this is genius! I made all my ingots in bread pans, which left a lot of little gaps to fill.
__________________
Ben
zartmancruising.com
Benz is offline   Reply With Quote
Old 05-04-2021, 04:34   #23
Registered User

Join Date: Dec 2009
Location: Australia
Boat: BUILT!!! Roberts Mauritius 43ft
Posts: 3,604
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by Benz View Post
Cooper, this is genius! I made all my ingots in bread pans, which left a lot of little gaps to fill.

Glad you like the idea!

It worked out very well as I could select the thickness and taper of each ingot. (The lead as laid would be very close to a solid block) The front compartments have 4 layers, mid about 3 layers and aft about two layers.

I had to do some cutting with my circular saw. I had a tarp under the saw to catch the "saw dust" which of course I poured into any little gaps.

Then I poured polyester resin to fill any gaps so the ingots couldn't move (and make the keel like a solid block. I then heavily fiber glassed over the top of the ballast.

But the trim ballast is loose and just laying there. Once the yacht is in the water I'll move the trim ballast to its permanent place and fiberglass over it just as I have done to the rest of the ballast.
coopec43 is offline   Reply With Quote
Old 05-04-2021, 05:15   #24
Registered User

Join Date: Dec 2009
Location: Australia
Boat: BUILT!!! Roberts Mauritius 43ft
Posts: 3,604
Re: Stolen ballast, how important is it really?

I should have mentioned all the "ingots" are laid fore and aft on their edge so that I could select tapered ones where the keel was narrowing. I did have photos of the laid ingots but then the camera carked it.
coopec43 is offline   Reply With Quote
Old 09-04-2021, 06:57   #25
Registered User

Join Date: Feb 2010
Location: New Orleans, LA
Boat: Figment 40
Posts: 9
Re: Stolen ballast, how important is it really?

Islander 28 is a Bob Perry design. One of his best, so. Congratulations on getting a nice boat. I suggest you reach out to the "Maestro" on the FB page "Friends of Bob Perry, Yacht Designer, Fan Club" page. I'm sure he can tell you a lot about the ballast.
eddiestubbs is offline   Reply With Quote
Old 09-04-2021, 07:29   #26
Registered User
 
capn_billl's Avatar

Join Date: Aug 2010
Location: Naples, FL
Boat: Leopard Catamaran
Posts: 2,572
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by Jim Cate View Post
Adding 200 lbs at the top of the existing 3000 lb ballast will not, IMO, have a "great effect" on the righting moment... one that the PO will be able to discern in his use of the boat.

Jim
Depends on hull curvature.

Boats have capsized from deviating too far from designed waterline.
capn_billl is offline   Reply With Quote
Old 09-04-2021, 07:47   #27
Registered User

Join Date: Feb 2013
Location: WY / Currently in Hayes VA on the Chesapeake
Boat: Ocean Alexander, Ocean 44
Posts: 1,149
Re: Stolen ballast, how important is it really?

Quote:
Originally Posted by eddiestubbs View Post
Islander 28 is a Bob Perry design. One of his best, so. Congratulations on getting a nice boat. I suggest you reach out to the "Maestro" on the FB page "Friends of Bob Perry, Yacht Designer, Fan Club" page. I'm sure he can tell you a lot about the ballast.
This.... It would be well worth a consultation fee to get it right!
darylat8750 is offline   Reply With Quote
Old 09-04-2021, 09:09   #28
Registered User

Join Date: Jul 2013
Posts: 6
Re: Stolen ballast, how important is it really?

Hi Skkeith,

I too have an I28 with funky keel bolts. Could you share how you plan to sister the keel bolts? My understanding is that the lag bolt method is not very secure due to the malleability and creep of the lead against the threads. I was contemplating drilling down for a threaded rod and then sideways into the keel to form a nut pocket.
Grey Goat is offline   Reply With Quote
Old 09-04-2021, 13:44   #29
Registered User

Join Date: Feb 2013
Location: traveling
Boat: Islander 32
Posts: 27
Re: Stolen ballast, how important is it really?

Maybe a little off topic but as was mentioned that the balast up so high wouldnt help your righting moment. Maybe look into adding a fin on the bottom of your keel. If you want that effect maybe a good idea but if you are just a weekend user continue with your plan.

Im curious, though, i have a 1979 islander 32 and couldnt be happier. I consistently get 4 - 6 knt. With the genoa alone in fairly light air. Why is your islander a mistake???
oldbuzzard is offline   Reply With Quote
Old 09-04-2021, 15:20   #30
Registered User

Join Date: Mar 2020
Location: Hamble
Posts: 33
Re: Stolen ballast, how important is it really?

Are there no engineers on here?


Adding ballast in the centre of the boat changes the polar moment of the boat, thus changing pitching period.


Ballast added internally doesn't greatly affect heel at low angles, but as heel increases, the distance from ballast to heeled centre of buoyancy increases until(sometimes) past 90degrees.Many trailer sailers have small light centreboards/keels, and rely on internal ballast to stop capsizing.


A lost mast will not capsize the boat. If anything,a sailboat with mast removed would end up nearly unable to be capsized.


All just common sense.



There was a mention about the 79 Fastnet. I was there, on an Admiral's Cup team boat. No raceboats were lost, but a few were forced to be abandoned then picked up by local trawlers. The couple of boats that were lost were cruisers of poor design, and took on water when excessively heeled but not as far as 90degrees.


In IOR raceboat days, lead ballast, sometimes in large amounts, was used to trim the boats to affect immersion depths, thus affecting rating(or handicap) Bow down trim was encouraged by the rule, but made the boats pigs to sail.
Elleroo is offline   Reply With Quote
Reply

Tags
import

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
I DID SOMETHING REALLY, REALLY, STUPID zengirl Plumbing Systems and Fixtures 60 04-08-2019 11:37
Too good to be true? Really, really cheap BlueCharts skipmac Navigation 2 22-12-2014 19:09
Balast in a Prout 35. Mike T Multihull Sailboats 21 18-08-2012 20:52
Some Ads Are Really Really Slow . . . Catamount Forum Tech Support & Site Help 3 15-01-2011 10:05
Stolen Benetau seafox Health, Safety & Related Gear 17 18-10-2006 22:41

Advertise Here


All times are GMT -7. The time now is 05:24.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.